You don't need to spend almost $200.00 on Kenko tubes. You can get AF tubes for like $25.00 including shipping that will do the same job.
extension tubes | eBay
A Timer remote or shutter release so that there is no movement from the camera is good to have with macro. Those are fairly cheap too on Ebay...
Ehhh... I would NOT recommend this as an option. My brother bought a set exactly like this, thinking they looked like a good deal. Mounted one tube just to see what it was like, and wound up taking it to a camera repair shop where they had to CUT if off of the camera because the mount was so poorly machined that it would not come off any other way. Fortunately, the camera was fine, but between the cost of the tubes and the trip to the shop, he could have bought a set of Kenko tubes and had enough left over for a large cup of coffee. Kenko tubes are very well made and I've never had any issues at all with mine. There is a reason that some things cost what they cost. Caveat emptor and all that jazz....